Filters are used to remove impurities from a flow of fluid such as a liquid or a gas. The filter will typically include porous filter media that traps the impurities as the fluid flows through the filter media.
One particular type of media is a fluted type media that is formed from a plurality of adjacent layers of filter media. The layers define a plurality of flutes that form either inlet or outlet flutes depending on which flutes are open at an inlet side and closed at the outlet side or closed at the inlet side and open on the outlet side of the filter. Typically, the layers of media are formed from a facer sheet secured to a corrugated or fluted sheet. This composite structure can then be wound to form a plurality of adjacent layers from a single continuous strip or can be cut into segments and then stacked to form a plurality of adjacent layers.
A seal arrangement is also typically attached to the filter media to releasably seal the filter media within a housing. This seal can be a radially directed seal or an axially directed seal. Typically, the seal is a relatively soft and compliant material so that it forms a good fluid tight seal with a corresponding surface of the housing. The seal arrangement is typically attached to an outer peripheral surface of the media.
A pressure differential will exist across the filter media to force the fluid to flow through the media. In many systems, the pressure differential is generated by a vacuum on a downstream side of the filter media. A vacuum across the media presents several problems, particularly with regard to the layered fluted type media.
This vacuum can cause radially inwardly directed compression of the filter media reducing the size of the outer periphery of the media. This reduction in size can cause several problems. This can cause the compliant seal to be drawn radially inward as well. If the seal is a radially directed seal, this can cause the seal to disengage from the housing sealing surface and create a leak path or, at a minimum, reduce the quality of the seal between the seal arrangement and housing.
Further, if the seal is an axial seal, the seal arrangement is often axially pinched between portions of the housing. When the filter media reduces in size while the seal is held firm between portions of the housing, this can cause the connection between the seal arrangement and media to become destroyed. Alternatively, it can cause the layers of the filter media to separate. Either of these problems can create undesirable leak paths.
A further problem particularly related to fluted media is that the pressure differential across the filter media can cause the adjacent layers to slip relative to one another, which is often referred as telescoping. This telescoping of the media can also create leak paths. Further, when the layers telescope, the problems relating to vacuum discussed above can be exacerbated.
Another type of media is pleated media that is typically a single continuous piece of filter media that is folded to form a plurality of adjacent panels interconnected by the folds. The interconnected panels form a plurality of peaks and valleys. One problem with this form of media is that the peaks on an inlet side of the filter may be directly exposed to impingement of impurities as well as another action that can cause cracking or damage to the filter media at the peaks.
Embodiments of the present invention are aimed at rectifying one or more of these problems or otherwise providing improvements over the art.